This paper addresses two related problems in the context of transparent optical networks. In the network design problem, the aim is to identify a set of fiber links to connect a given set of nodes. In the network upgrade problem, the aim is to identify a set of new fiber links to add to a given network topology. For a given fiber length budget, the aim in both problems is to maximize the network resilience to the simultaneous failure of its critical nodes. The resilience is evaluated by the average 2‐terminal reliability (A2TR) against a set of critical node failures and the critical nodes are the ones that minimize the A2TR of the network. So, the design/upgrade problem is a bi‐level max‐min optimization problem. Recently, a multi‐start greedy randomized heuristic was proposed for both problems. Here, we propose an alternative method based on a greedy deterministic algorithm and we provide computational results showing that the new method obtains better solutions. The results show that the resiliency difference between existing network topologies and the best network design solutions is very high but this difference can be significantly reduced by network upgrades with small fiber length budgets.

中文翻译：

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透明光网络拓扑的设计/升级，可以抵抗其关键节点的同时故障

本文解决了透明光网络中的两个相关问题。在网络设计问题中，目标是确定一组光纤链路以连接给定的节点集。在网络升级问题中，目标是确定一组新的光纤链路以添加到给定的网络拓扑中。对于给定的光纤长度预算，这两个问题的目的都是最大化网络对其关键节点同时发生故障的弹性。通过针对一组关键节点故障的平均2终端可靠性（A2TR）评估弹性，关键节点是使网络A2TR最小的节点。因此，设计/升级问题是双层最大-最小优化问题。最近，针对这两个问题都提出了多起点贪婪随机启发式算法。这里，我们提出了一种基于贪婪确定性算法的替代方法，并提供了计算结果，表明该新方法获得了更好的解决方案。结果表明，现有网络拓扑与最佳网络设计解决方案之间的弹性差异非常大，但是可以通过使用较小的光纤长度预算进行网络升级来显着减小这种差异。